1. Field of the Invention
The present invention of the application relates to an infrared sensor. More particularly, the present invention relates to an infrared sensor having a wide viewing angle and detecting infrared radiation, and to an infrared sensor having improved electromagnetic shielding characteristics.
2. Description of the Related Art
As one type of related infrared sensor used in, for example, human body detection and crime-preventing devices, the following infrared sensor with lead terminals is provided. As shown in FIG. 6, in the infrared sensor, an infrared sensor element 53 having light-receiving electrodes 61 disposed on a pyroelectric element 62 is supported on a metallic base (stem) 52 having lead terminals 51. In addition, the infrared sensor element 53 is accommodated in a cylindrical metallic case (cap) 55 including an optical filter 54 provided at the upper surface side of the case 55 and transmitting infrared radiation. Further, the infrared sensor ordinarily includes a supporting table 63, a substrate 64, a bypass capacitor 65, an FET 66, and a resistor 67. The supporting table 63 supports the infrared sensor element 53. The substrate 64 has the supporting table 63 placed thereon, and has necessary electrodes and circuits (not shown) provided on its surface. The input/output lead terminals 51 (51a and 51b) of the infrared sensor pass through the metallic stem 52 through an insulating material 60, and are connected to the circuits on the substrate 64. The ground lead terminal 51 (51c) is electrically connected to the stem 52.
As a mounting structure (mounting method) for mounting the optical filter to the metallic case (cap) in such type of infrared sensor, the following mounting structure (mounting method) is proposed. For example, as shown in FIG. 7, the mounting structure (mounting method) is such that the optical filter 54 is disposed at an opening window 58 of the metallic case 55 so that the outer surface of the optical filter 54 and the outer surface of the metallic case 55 are flush with each other. In addition, edges of the optical filter 54 and edges defining the opening window 58 are adhered and secured to each other with a conductive adhesive 57. See, for example, Japanese Unexamined Patent Application Publication No. 9-79902.
However, in the infrared sensor in the aforementioned Japanese Unexamined Patent Application Publication No. 9-79902, the optical filter 54 is fitted to a portion (opening window) 58 of the top surface of the metallic case 55. Therefore, the entire top surface of the metallic case 55 does not become a light-receiving surface. As a result, an infrared light-receiving area (viewing angle) becomes narrow.
As another type of infrared sensor, the following infrared sensor is proposed. As shown in FIG. 8, in the infrared sensor, an optical filter 71 is held by shelves 73, formed at a conductive inner-peripheral heat-transmitting covering member 75, disposed at an inner peripheral portion of a conductive protecting member (package) 72. In addition, using a conductive adhesive 74, end surfaces of the optical filter 71 are joined to an inner peripheral surface of the conductive inner-peripheral heat-transmitting covering member 75, and the bottom surface of the optical filter 71 is joined to the bottom surfaces of the shelves 73, formed at the conductive inner-peripheral heat-transmitting covering member 75. As a result, the optical filter 71 is electrically connected to the conductive protecting member (package) 72, so that electromagnetic shielding characteristics are enhanced. See, for example, Japanese Unexamined Patent Application Publication No. 8-15007.
However, the structure of the infrared sensor discussed in Japanese Unexamined Patent Application Publication No. 8-15007 is provided to increase electromagnetic shielding characteristics and to reduce the influence of an ambient temperature change on an infrared sensor element. As illustrated in FIG. 9 (illustrating an embodiment disclosed in Japanese Unexamined Patent Application Publication No. 8-15007), when the infrared sensor has a structure in which portions of a metallic plate 81, which becomes the conductive inner-peripheral heat-transmitting covering member 75, are bent to form the shelves 73 at substantially central portions of the respective sides, the shelves 73 restrict the viewing angle of the optical filter 71 (see FIG. 8). Therefore, the infrared sensor cannot provide a viewing angle with maximum efficiency.